Pigmented coating compositions containing liquid alkyl polysiloxane



Patented Sept. 19, 1950 PIGMENTED COATING COMPOSITIONS CON TAININGLIQUID ALKYL POLYSILOXANE Craig M. Saga-Schenectady, N. Y., assignor toGeneral Electric Company, a

New York No Drawing.

11 Claims.

' of matter exhibiting a decreased tendency to pigment flotation, thesaid composition comprising (1) a pigmented resinous coating compositionand (2) from 0.000001 to 0.01 per cent, by weight,

based on the weight of the coating composition (1. e.,onthe total weightof the resin and pigment) ,of a liquid alkyl (e. g., a lower alkyl, forinstance, methyl, ethyl, propyl, isopropyl, butyl, amyl, etc.)polysiloxane.

One of the objects of this invention is to prepare pigmented resinouscoating compositions having good pigment anti-flotation properties.

Another object of this invention is to eliminate the tendency ofpigmented coating compositions to ,exhibit "silking and "flow lines.

A further object is to produce pigmented resinous coating compositionswhich yield smooth surfaces without the danger of the appearance of whatis known as "orange peel in the surface.

Other objects of this invention will become more apparent as .thedescription thereof, proceeds.

corporation of Application December 29, 1947, Serial No. 194,443

sion characteristics of the protective coating. In

- addition, the presence of the liquid alkyl poly- Heretofore, the useof pigmented resinous coat- I ing compositions has often beenaccompanied by the appearance of several defects in the coated surfaceafter the coating composition has dried. Among these defects has beenthe tendency of the coating to exhibit pigment flotation, i. e., theappearance of streaks of pigment in the coated surface. Another defectoften resulting from the use of the aforementioned pigmented protectivecoatings has been the appearance of flow lines caused by the poorleveling of the coating composition. Finally, lacquers and bakingenamels have often exhibited rough and uneven surfaces commonly referredto in the art as an "orange peel surface.

I have now discovered that all the foregoing defects frequentlyencountered in connection with the use of pigmented resinous protectiveor decorative coatings may be avoided by incorporating in the saidcoating composition a small amount (e. g., from 0.000001to 0.01,preferably from 0.00001 to 0.001, per cent, by weight, of the totalweight of the resin and pigment in the coating composition) of a liquidalkyl polysiloxane, preferably, a methylpolysiloxane, having analkyl-to-silicon ratio of from 1.95 to 2.2 alkyl groups per siliconatom, more particularly from i 1.98 to 2.1 or even 2.0 alkyl groups persilicon atom. The elimination' of the above-described defects is notaccompanied by any perceptible detrimental effect on the drying rate oradhesiloxane seems to improve the pigment wetting and water-resistanceof the said coating composition.

The liquid alkyl polysiloxanes found suitable in effecting theabove-described improvements in the properties of the pigmented coatingcomposition are those obtained, for example, by the hydrolysis of analkylhalogenosilane, e. g., a methylhalogenosiiane, for instance, pureor substantially pure dialkyl-substituted dichlorosilane, e. g.,dimethyldichlorosilane, or an alkyl-substituted, e. g.;methyl-substituted silane (the methyl groups being joined to the siliconatom through carbon atoms), whose other valences are satisfled byradicals which themselves are readily hydrolyzable, for instance,hydrogen, amino, alkoxy, aroxy, acyloxy, etc., radicals. The termsliquid alkyl polysiloxane and liquid methyl polyto about 5 (preferablyfrom 0.1 to 2) mol per cent methyltrihalogenosilane, more specificallymethyltrichlorosilane, is hydrolyzed in manners now well known in theart. Stated alternatively, with regard to the use of certain liquidmethyl polysiloxanes found desirable in the practice of my claimedinvention, they may be, considered as being comprised of liquidpolymeric dimethylsiloxane containing up to 5 mol per cent, preferablyfrom 0.1 to 2 mol per cent, copolymer- -ized monomethylsiloxane.

The oily hydrolysis product may then be fractionally distilled to removethe low boiling materials (trimers, tetramers, etc.) thereby obtainingthe higher molecular weight liquid methyl polysiloxanes, which may thenbe added (advantageously in the form of a dilute solution using asolvent miscible with the film-forming ingredients, e. g., aromatic andaliphatic hydrocarbons, etc.) to the particular pigmented resinouscoating composition. If desired, the hydrolyzed mixturesof hydrolyzabledimethyl-substituted silanes, either among themselves or with other-'hydroly zab1e silanes containing, for example, one methyl groupsubtituted 6n the silicon atom, for instance, methyltrichlorosilane, maybe caused to react with, for example, hexamethyldisiloxane, in thepresence of sulphuric acid. More specific directions for the hydrolysisof hydrolyzable methyl-substituted alliance to form liquidmethylpolysiloxanes may be'found, for example, in Patnode applications, SerialNos. 463,813, now abandoned, 463,814, now Patent Number 2,469,888, and463,815, now abandoned,

wherein a preponderant number of valences of the silicon atoms aresatisfied by the substitution thereon by alkyl radicals.

Such intercondensations are accelerated by acidic materials, forexample, sulphuric acid, hydrochloric acid, ferric chloride, etc., aswell as by basic materials, for example, sodium hydroxide, potassiumhydroxide, etc. As a result of the hydrolysis and condensation, liquidalkyl-substituted polysiloxanes may be produced which may have on theaverage up to as high as 2.2 alkyl' groups substituted on each siliconatom. The liquid alkyl polysiloxanes prepared in this manner consistessentially of silicon atoms Joined together by oxygen atoms throughsilicon-oxygen linkages and alkyl radicals attached to silicon throughcarbon-silicon linkages, the remaining valences, if any, of the siliconatoms being satisfied by hydroxyl and/or by residual unhydrolyzedradicals such as the hydrolyzable radicals listed previously.

The pigmented resinous coating compositions whose properties may beefiectively improved by means of my claimed invention comprise liquidcoating compositions ordinarily employed as pigmented decorative orprotective surfacing compositions or enamels. These include, forexample, pigmented oil-modified alkyd resins, either alone or incombination with amido-aldehyde resins (i. e., aminoplast resins) e. g.,urea-formaldehyde, melamineformaldehyde resins, etc., pigmented coatingcompositions prepared, for example, from esters or ethers oi cellulose,for instance, ethyl cellulose, cellulose acetate, etc., nitrocellulose,oil-modified phenol-aldehyde resins, for instance: oil-modifiedpara-tertiary butyl phenol-aldehyde resins, etc., pigmented acrylic acidester resins, pigmented chlorinated rubber. compositions, as well as themamr other pigmented lacquers, enamels and Paints employed as decorativeand protective coatings.

My invention is particularly applicable in the case of modified (e. g.,oil-modified) alkyd resins. By the term modified alkyd resin as usedherein, I mean the resinous condensation product resulting from thereaction of one or more polyhydric alcohols with a polycarboxylic acid(or anhydride) and one or more of the following modifying ingredients,for instance, modifying oils, e. g.

4 fatty oils, fatty oil acids, etc., derived either from vegetable oranimal sources or produced synthetically, etc.-; esters, specificallyglycerides of fatty acids, etc.; and mixtures of one or more of thesemodifying ingredients with natural resins, as well as other equivalentproducts.

non-drying oils, semi-drying oils, drying oils, 76

Examples of polycarboxylic acids (or anhydrides) are oxalic, malonic,succinic, adipic, phthalic acid (or anhydride) halogenated phtha- 11cacids, for example, tetrachlorophthalic acid (or anhydride),4-chlorophthalic acid, isophthalic acid, etc.

Examples of polyhydric alcohols (.dihydric, trihydric, etc.) which maybe used in this invention are ethylene glycol, diethylene glycol,propylene glycol, glycerine, sorbitol, pentaeryrithrltol, etc.Monohydric alcohols, for example those boiling above C., such as alkylethers of glycols, for instance, alkyl ethers of ethylene and diethyleneglycol, etc., may also be used.

The modifying ingredients, including modifying oils in the raw, heated,or blown state, which may be employed in the preparation of the modifiedalkyd resins are, for example, linseed oil, chainawood oil, castor oil,soya bean oil, oiticica oil, linseed oil acids, coconut oil acids,palmitic acid, stearic acid, oleic acid, etc. The amount of themodifying ingredients may be varied within wide limits, for example,from 5 to '70 per cent, preferably from 10 to 60 per cent, by weight, ofthe total weight of the modifying ingredients, the polyhdric alcohol,and the polybasic acid or acids (or anhydride if used) present in thereaction mixture.

Equimolebular portions of the polyhydric alcohol and the polycarboxylicacid or anhydride may be used in making the modified alkyd resin. Iprefer to use at least a slight excess of the polyhydric alcohol inorder to cause the reaction to go more fully to completion. Techniquesfor making these modified alkyd resins will be clearl apparent fromprior work published in connection with alkyd resin preparations by themany workers in this art.

Among the various pigments which may be incor'porated in the resinouscoating compositions may be mentioned, for example, carbon black, lampblack, ferric oxide, titanium dioxide, lithopone, ferric hydroxide, zincchromate, zinc oxide, lead carbonate, lead chromate, silicates, forexample, manganese silicate, etc., ferric ferrocyanide blue, sulphates,arsenates, and other in organic salts, etc. v I

Theamount of pigment employed in the coating composition may be variedwithin wide limits depending on the application, the resin employed,

be practiced, the following examples are given by way of illustrationand not by way of limitation. All parts are by weight.

Example 1 A liquid methyl polysiloxane was prepared by hydrolyzingdimethyldichlorosilane containing about 6 to 8 mol per centmethyltrichlorosilane. The hydrolyzed liquid product was washed free ofacid, dried, and reacted with sufllcient hexamethyldisiloxane (in thiscase about 4 to 6 per cent, by weight, hexamethyldisiloxane) in theasaaoes presence oi sulphuric acid to yield a liquid methyl polysiloxanecontaining an average ratioo! from 1.98 to 2.11 methyl groups persilicon atom.

A portion of the flnally obtained liquid methyl polysiloxane wasdissolved in toluene in, the form or a l per cent, by weight, solution.

A modifled alkyd resin was prepared by heating a mixture comprising 20'parts soya bean oil acids, 10.5 parts glycerine, and 20 parts phthalicanhydride were heated for about 5 to 7 hours at around 225-250 C. in aninert atmosphere until an acid number of from 6 to 8 was obtained.

The'resin was cooled and dissolved in xylene to ing composition.

The above-prepared pigmented, oil-modified alkyd resin enamel, whenapplied by dipping to a metallic surface and the coatedsurface exposedto air for a short time immediately exhibited flotation of the pigmentas evidenced by streak- 0 ing or the surface.

To the aforementionedpigmented oil-modifled alkyd resin enamel was added1 per cent, by weight, based on the weight of the said enamel,

of a 1 per cent toluene solution of the liquid methyl polysiloxane.Another metal strip was dipped in this mixture andair-dried as before.

Thesurface of this sample was perfectly plain,

. smooth, and glossy and exhibited no pigment flotation.

Example 2 In this example, to 99 parts of the oil-modifled alkyd resinenamel (exhibiting pigment flotation) of Example 1 was added about 0.63part of a 1 per cent. by weight, toluene solution of a liquid methylpolysiloxane consisting of a mixture of linear methyl polysiloxanescontaining from 12 .to 16 carbon atoms and being repressented by thegeneral formula where n is a whole number equal to from 10 to 14. Use ofthis modified enamel resulted in a coated surface exhibiting no pigmentflotation.

Example 3 The productof hydrolysis of dimethyldichlorosilane wasisolated and amounts of this liquid oily product were added to theoil-modified alkyd resinous coating composition of Example 1, whichexhibited pigment flotation. When 0.001 per cent, by weight, of this oildissolved in toluene (based on the weight of the coating composition),was added, and the modified coating composition applied to a surface andallowed to dry, there was obtained a smooth, glossy film which showed noevidence of pigment flotation. The use of 0.01 per cent of this oil alsoreduced the pigment flotation. Amounts in substantial excess of 0.01 percent appeared to have no effect on pigment flotation.

Example 4 In this example, to a Chinawood oil-modified enamel pigmentedwith titanium dioxide and lamp black, which enamel exhibited pigmentflotation, was added about 1% per cent, by weight, based on the weightor the enamel, o! the 1 per cent liquid methyl polysiloxane solution.The addition of the aforementioned liquid methyl polysiloxane resultedin elimination of the pigment flotation.

- Example 5" In this example, the same enamel was employed as in Example2 with the exception that the pigment was red iron oxide instead of thetitanium dioxide and lamp black used in Example 4. This pigmentedenamel, which showed strong evidence of pigment flotation, was renderedcompletely acceptable as to clearness and smoothness of the surface bythe addition thereto of the same amount of liquid methyl polysiloxane asemployed in Example 4.

Example 6 A titanium dioxide-pigmented chlorinated rubher-phenolic resincoating composition exhibiting pigment flotation was rendered acceptableand the pigment flotation eliminated by the addition to the enamel ofabout the same amount, by weight, of the liquid methyl polysiloxaneemployed in Example 4.

Example 7 A carbon-black pigmented, soya Foean oil-modifled alkyd resinenamel modifled with about 15 per cent, by weight, of a butylalcohol-modified melamine-formaldehyde resin, which showed 5 undesirableorange peel" characteristics on application to a flat surface, wascorrected and this ,orange peel eliminated by th addition thereto ofabout 1 per cent, by weight, of the 1 per cent toluene solution of theliquid methylpolysiloxape prepared in Example 1. The surface obtainedwas smooth and free of any surface defects.

Although the foregoing examples disclose the use of various resinouscoating compositions together with a particular liquid methylpolysiloxane to obtain the desired properties of the pigmented resinouscoating composition, it will, of course, be apparent to those skilled inthe art that other pigmented coating compositions exhibiting pigmentflotation, as well as other liq- .uid alkyl polysiloxanes, many examplesof which have been disclosed previously, may be employed .in place ofthe foregoing enamels or coatings and .pigmented resinous 'coatingcompositions exhibiting a decreased or no tendency towards pigmentflotation, but it is also possible to reclaim pigmented coatingcompositions rejected because of pigment flotation and make themacceptable as coating agents.

In addition to the liquid alkyl polysiloxanes disclosed above, I havealso found that pigment flotation can be reduced and eliminated inpigmented resinous coating compositions by using such materials as, forexample, dimethyl germanium sulfide [(CHaMGeS], the preparation of whichis more particularly disclosed and claimed in Rochow application SerialNo. 791,664, now Patent Number 2,506,386, filed December 13, 1947, andassigned to the same assignee as the present invention; as well as apolymeric para-tertiary butyl phenol-formaldehyde resin 15 compositionof matter containing in its moaoaaoco lecular structure. a plurality ofsilicon atoms linked directly to each other, each silicon atom bearingonly two methyl groups, and a plurality of silicon atoms linked to eachother through oxygen atoms where each silicon atom has two methyl groupsattached thereto, the said composition containing about 2 per centchlorine. The following example illustrates more particularly the methodof preparation of the latter one of these anti-flotation agents and itsuse in pigmented resinous coating compositions to eliminate pigmentflotation.

Example 8 About 454 parts sodium metal was placed in a pressure bombtogether with 866 parts dry xylene and 645 parts dimethyldichlorosilane.action temperature rose autogenously up to about 200 C. and thensubsided. The bomb was then heated for about 6 hours at 115 C. Thexylene- -soluble material present in the reaction mixture wasfractionally distilled and thatfraction remaining as a residue after allvolatile material boiling up to 300 C. at 3 mm. pressure was isolated.Analysis of this compound showed that it was a polymeric composition ofmatter comprising a plurality of CH: CH;

I H1 H3 linkages and a plurality of on on:

Ha Ha linkages and containing about 2 per cent chlorine. .A sample ofthis polymeric material was dissolved in toluene to make a l per cent,by weight, solution.

One per cent, by weight, of the foregoing toluene solution was added tothe oil-modified alkyd resin coating composition comprising a castoroilmodified glyceryl phthalate resin modified with about 20 per cent, byweight, of a butylated melamine-formaldehyde resin, and the said coatingcomposition was applied by dipping to a flat surface. When thissurface'was air-dried there was obtained a glossy, smooth film whichexhibited no evidence of pigment flotation.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In the process for decreasing the tendency of a pigmented resinouscoating composition selected from the class consisting of pigmentedoilmodified alkyd resins and pigmented oil-modified phenol-aldehyderesins to exhibit pigment flotation, the step which comprises adding tothe aforesaid coating compositions and mixing thereinfrom 0.000001 to0.01 per cent, by weight, based on the weight of the coatingcomposition, of a liquid alkyl polysiloxane having an average of from1.95 to 2.2 alkyl groups per silicon atom.

2. In the process for decreasing the tendency of a pigmented coatingcomposition selected from the class consisting of pigmented oil-modifiedalkyd resins and pigmented oil-modified phenol-aldehyde resins toexhibit pigment flotation, the step which comprises adding to theaforesaid coating compositions and mixing therein from 0.000001 to 0.01per cent, by weight, based on the weightof the coating composition, of aliquid methylpolysiloxane containing an average of from 1.95 to 2.2methyl groups per silicon atom.

3. In the process for decreasing the tendency of a pigmentedoil-modified alkyd resinous coat- I 0.000001 to 0.001 per cent, byweight, based on The rethe weight of the coating composition, of aliquid polymeric dimethylsiloxane containing up to 5 mol per centcopolymerized monomethylsiloxane and having an average of from 1.95 to2.2 methyl groups per silicon atom.

4. In the process for decreasing the tendency of a pigmentedoil-modified phenol-aldehyde resinous coating composition to exhibitpigment flotation, the stepwhich comprises adding to the aforesaidcoating compositions and mixing therein from 0.000001 to 0.001 per cent,by weight, based on the weight of the coating composition, of a liquidpolymeric dimethylsiloxane containing up to 5 mol per cent copolymerizedmonomethylsiloxane and having an average of from 1.95

to 2.2 methyl groups per silicon atom.

5. In the process for decreasingthe tendency of a pigmentedoil-modified, amide-aldehydemodifled alkyd resinous coating compositionto exhibit pigment flotation, the step which comprises adding to theaforesaid coating compositions and mixing therein from 0.000001 to 0.001per cent, by weight, based on the weight of the coating composition, ofa liquid polymeric dimethylsiloxane having a methyl-to-silicon ratio offrom 1.98 to 2.2 and containing from 0.1 to 2 mol per cent copolymerizedmonomethylsiloxane.

6. A pigmented coating composition selected from the class consisting ofpigmented oil modifled alkyd resins and pigmented oil-modifiedphenol-aldehyde resins exhibiting a decreased tendency to pigmentflotation, the said coating composition having incorporated therein from0.000001 to 0.01 per cent, by weight, based on the weight of the coatingcomposition, of a liquid alkyl polysiloxane having an average of from1.95 to 2.2 alkyl" groups per silicon atom.

7. A composition of matter exhibiting good resistance to pigmentflotation, said composition comprising (1) a pigmented resinous coatingcomposition selected from the class consisting of pigmented oil-modifiedalkyd resins and pigmented oil-modified phenol-aldehyde resins and (2)from 0.000001 to 0.01 per cent, by weight, based on the weight of thecoating composition, of a liquid methylpolysiloxane containing anaverage of from 1.95 to 2.2 methyl groups per silicon atom.

8. A composition of matter exhibiting good pigment anti-flotationproperties, the said composition comprising (1) a pigmented oil-modifiedalkyd resinous coating composition and (2) from 0.000001 to 0.001 percent, by weight, based on the weight of the coating composition, of aliquid polymeric dimethylsiloxane containing up to 5 mol per centcopolymerized monomethylsiloxane and having an average of from 1.95 to2.2

-methyl groups per silicon atom.

9. A composition of matter exhibiting good pigment anti-flotationproperties, the said composition comprising (l) a pigmented oil-modifiedphenol-aldehyde resinous coating composition and (2) from 0.000001 to0.001 per cent, by weight, based on the weight of the coatingcomposition, of a liquid polymeric dimethylsiloxane containing up to 5mol per cent copolymerized monomethylsiloxane and having an average offrom 1.95 to 2.2 methyl groups per silicon atom.

spasms 10. A pigmented composition or matter exhibiting good pigmentanti-flotation properties, the said composition comprising (1) apigmented oil-modified, amido-aldehyde-modiiied alkyd resinous coatingcomposition and (2) from 0.000001 to 0.001 per cent, by weight, based onthe weight of the coating composition, of a liquid methyl polysiloxanecontaining an average ratio of from and pigmented oil-modifiedphenol-aldehyde u resins and (2) from 0.000001 to 0.01 per cent, byweight, based on the weight or the coating composition, or thehydrolysis product or dimethyldi- REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATEN'I'S Name Date Larsen May 1, 1945 I OTHER REFERENCESRochow, Chemistry of The Silicones, Wiley,

Number 1 1946, pages 64 and 65.

Bass, Chemistry and Industry, April 5, 1947, pp. 171 and 1'14.

1. IN THE PROCESS FOR DECREASING THE TENDENCY OF A PIGMENTED RESINOUSCOATING COMPOSITION SELECTED FROM THE CLASS CONSISTING OF PIGMENTEDOILMODIFIED ALKYD RESINS AND PIGMENTED OIL-MODIFIED PHENOL-ALDEHYDERESINS TO EXHIBIT PIGMET FLOTATION, THE STEP WHICH COMPRISES ADDING TOTHE AFORESAID COATING COMPOSITIONS AND MIXING THEREIN FROM 0.000001 TO0.01 PER CENT, BY WEIGHT, BASED ON THE WEIGHT OF THE COATINGCOMPOSITION, OF A LIQUID ALKYL POLYSILOXANE HAVING AN AVERAGE OF FROM1.95 TO 2.2 ALKYL GROUPS PER SILICON ATOM.